The invention relates to a semiconductor device comprising a substrate of a first conductivity type having a high doping concentration c.sub.o, a first epitaxial surface layer of said first conductivity type and having a lower doping concentration c&lt;c.sub.o, a surface adjacent zone of the second conductivity type opposite to the first conductivity type forming with said epitaxial surface layer a main planar pn junction having over the major part of its area a junction depth x.sub.j, and a structure of floating guard rings of said second conductivity type.
It also relates to a class of devices of the kind described above, each device of the class being defined by a maximum operating voltage V. Finally, the invention relates to a method of manufacturing such a class of devices.
The invention can be very advantageously used in the field of devices such as rectifier diodes, field effect transistors, bipolar transistors, thyristors and especially power devices operating at high voltages.
A semiconductor device as defined above is described in European Patent Application Publication No. 0115093. This device is constituted by a main (planar) junction enclosed by guard rings which permit increasing the breakdown voltage in the vicinity of the surface of the epitaxial surface layer deposited directly on the highly doped substrate. The thickness and the concentration c of this layer are determined in such a manner that the breakdown voltage through the layer is higher than the maximum operative voltage V and the resistance in the "on" state is a minimum. The structure of guard rings, that is to say their number, their width and their relative distance, is calculated as a function of the depth x.sub.j of the main pn junction, the concentration c of the epitaxial layer and the desired maximum operating voltage. This structure is reproduced on a doping mask which serves to form simultaneously the main pn junction and the floating guard rings.